Scientists believe that
Paroxysmal nocturnal hemoglobinuria (PNH) is an ultra-rare bone marrow failure disease in which red blood cells break apart. Normal red blood cells have a shield of proteins that protect them from coming under attack by the body's own immune system. PNH occurs because that protein shield is missing. PNH is often associated with reduced bone marrow function (low blood counts) caused by aplastic anemia.